Function works, but breaks used in Class

Question

I have this function I use over and over in my applications
(Addins is but one item I have to do this to):
private function doAddins():void {
var _addIns:Array = [];
var _len:uint = app._chosen2.length;
for (var i:int=0; i<_len; i++) {
var _m:String = app._chosen2
.@sn;
_addIns.push(_m);
Where "_chosen2" is an ArrayCollection defined in the main
application file. Obviously, it loops through this array collection
and makes an array out of all the "sn" attributes. It works
perfectly.
So I figured I'd add it to my Utilities class file, as a
static function, like:
public static function getSNs(a:ArrayCollection):Array {
var _arr:Array;
var _len:uint = a.length;
for (var i:int=0; i<_len; i++) {
var _m:String = a.@sn;
_arr.push(_m);
return _arr;
And then I call it like : Utitlies.getSNs(app._chosen2);
But it bombs out with an error that I am trying to coerce an
array out of an array collection. Why?

Answer 1

In the second function, you are declaring the variable _arr
as an Array, but you are not setting it. This could be part of it.
var _arr:Array = new Array();